1. Field of This Invention
This invention relates to a process for producing 4-hydroxy-phenyl-1, 3-dioxo-2-indenylidene-acetonitrilies, to such compounds themselves and to the use of such compounds.
2. Prior Art
Indicator action utilizes the fact that certain compounds have different colors at different hydrogen ion concentrations. Such indicators find use in analytical chemistry.
A neutralization indicator is a substance which possesses different colors in acid and alkaline solutions.
Anthraquinone, which is colorless, is: ##SPC3##
A number of the derivatives of anthraquinone are important in the dye industry, for example, as dye intermediates. The alizarin derivatives are mordant and acid dyes.